Method and apparatus for diluting rosin size



Oct. 30, 1951 E. A, HOWELL METHOD AND APPARATUS FOR DILUTING ROSIN SIZE Filed Jan. 3l, 1951 Patented Oct. .30, 1951 METHOD AND APPARATUS FOR DILUTING ROSIN SIZE Edgar A. Howell, New York, N. Y., assignor to American Cyanamid Company, New York, N. Y., a corporation of Maine Application January 31, 1951, Serial No. 208,677

3 Claims.

This invention relates to a method and apparatus for diluting rosin sizes from concentrated dispersions to the dilute aqueous condition in which they are used in paper mills. The invention includes a twostage dilution and homogenization of the rosin size as well as the novel apparatus or system provided therefor, including certain safety features, that will hereinafter be more fully described.

Rosin sizes are usually produced by saponifying wood rosin, gum rosin, tall oil rosin or other types of abietic acid with alkalies. In preparing liquid rosin sizes the rosin is ordinarily heated with an aqueous solution of sodium or potassium carbonate, usually employing about 9-16% of the carbonate, based on the weight of the rosin, at about 190-212" F. for' about 6 hours. In the preparation of dry rosin size the rosin may be reacted with about 9-12% of sodium or potassium hydroxide in the form of a relatively concentrated aqueous solution, which produces the dry rosin size directly, or a liquid size may be evaporated on a drum drier or by spray drying.

Liquid rosin sizes are usually sold to paper mills at concentrations of about rI80% solids, the liquid portion being either all water or, in some cases, with the addition of a small proportion of ethanol, ethylene glycol or other alcohol. The dilution of these concentrated sizes has heretofore presented a denite problem, for the size goes through a gel stage upon dilution with cold water and is more viscous at intermediate concentrations of, for example, 30-40% solids than it is at '7D-80% solids. It is necessary, therefore, to heat the concentrated rosin size solution and A to dilute it initially with hot water until a concentration below the gel stage is obtained; with most sizes a safe limit of dilution with hot water is about 1020% solids. Further ldilution may then be made with cold water until the concentration is reached at which the size is to be mixed with the paper pulp, this concentration usually being about 1-5% solids.

The present invention has as a principal object the provision of a method whereby concentrated liquid rosin sizes are heated and diluted continuously and automatically with hot water to the desired gel-free intermediate concentration and are finally homogenized to produce a uniform dispersion after which they are further diluted with cold Water and again homogenized to form the finished dilute rosin size having a concentration suitable for use in a paper mill. A further object of the invention resides in the provision of an apparatus for carrying out this heating, dilution and homogenization. A still further important feature of the invention resides in the provision of safety interlocks between the various elements and sub-combinations of apparatus whereby damage to the system or to the size is avoided in case of failure of any of the component parts. The importance of the above and other objects of the invention will become apparent from the following description of a preferred embodiment thereof, when taken'with the appended claims.

The invention will be further described with reference to the accompanying drawings, wherein Fig. 1 is a diagrammatic illustration of a dilution systemv in accordance with the invention. Fig. 2 is a vertical section of a Venturi mixer for diluting the liquid rosin size with hot water, and Fig. 3 is a similar section of a constant backpressure valve employed in practicing the process.

Referring to Fig. 1 of the drawings, a, concen-Y trated liquid rosin .size which may be, for example, of solids, is fed into a constant delivery pump l from a storage tank that is not shown. This pump may be, for example, a gear pump of from gallon to 3 gallons per minute capacity. The rate of discharge of size from the pump is adjusted by a manually operated speed control 2 which is adjusted in accordance with the quantity of dilute rosin size required by the paper mill. The pump operates against a constant back-pressure valve 3, constructed as shown in Fig. 2 and to be described later, from which the size is passed through pipe I into a heater 5. In this heater, which may advantageously be of the spiral plate type, the size is heated to a temperature within the dilution range, which may lie within the temperature range of from about 140 F. to about 200 F. or higher. It will be understood that different types of sizes may have different temperatureviscosity curves during dilution; however, in practically all cases gel formation can be offset by diluting at temperatures above about 140 F. In the particular system illustrated, 170 F. has been selected as the dilution temperature as this temperature provides a considerable margin of safety and is easily attained in the system described.

The system for maintaining a constant supply of hot water having a definite temperature, and of delivering this hot water at a constant but ladjustable rate, constitutes an important feature of the invention. A hot water tank I0, which ls provided with a mat-controlled inlet valve II for cold water, may advantageously be of 50 gallons capacity. Water from this tank is withdrawn constantly through a lower line I2 by a pump I3 and passed through a steam injector I4' after which it may recirculate back to the tank I through line I provided with a manually adjustable constant back-pressure valve I6. The steam is supplied through line I1 and valve I8, which i/sna thermostatically controlled valve that operates in response to the temperature of the water in line I5 as indicated by the dotted line I9. By introducing the steam into a recirculating side line in this manner, the development of steam hammering is eliminated.

Constant delivery of hot water from the storage tank I0 is obtained by operation of the pump I3 against the constant -back pressure of the valve I6 which my be set (for example) at '10 pounds pressure. The setting of this valve determines the maximum back pressure of the pump system, since a higher back pressure will cause the valve to open. The hot water is withdrawn from the system by way of pipe 2l) through a high lift V-port manually adjusted valve 2I, whereby the rate of flow is adjusted to the amount indicated on a ow meter 22. The capacity of the pump I 3 is substantially larger than the maximum now of water to be withdrawn through valve 2I, so that some water is always, recirculated through valve I6 and line I5 maintaining a constant back pressure, and therefore a constant flow of hot water is always obtained through the valve 2l and meter 22.

Uniform mixing of a constant flow of rosin size from the heater 5 with a constant flow of hot water from the tank I0 is obtained by means of a Venturi mixer 25, the structure of which is shown in Fig. 2 of the drawings. Reference to this gure will show that the hot water, introduced through inlet 25, is directed through nozzle 21 into the throat of a. Venturi tube 28. Meanwhile the hot rosin size solution is admitted through inlet 29 and passes uniformly into the ared end 30 of the venturi. Uniform mixing is obtained by the turbulence created within the restricted portion of the tube 28, and the resulting diluted size dispersion is discharged through outlet 3l into pipe 32. Experience has shown that a highly uniform dispersion of diluted rosin size is obtained by this procedure.

The diluted rosin size dispersion obtained from lthe Venturi mixer 25 is homogenized to free it from lumps or other manifestations of gel formation by passage through a constant back-pressure valve 34 having the structure shown in Fig. 3 of the drawings. Referring to this figure it will be seen that constant back pressure is obtained by the force of a disc 35 working against the upper edge 36 of an outlet pipe 31. The rosin size dispersion is admitted through inlet 38 and passes upwardly through pipe 33 into an annular chamber 40 that surrounds the disc 35. Constant back pressure is obtained by the force of a springpressed plunger 4I, which presses'by means of diaphragm washer 42 and diaphragm 43 upon the disc 35. Passage of the rosin size between the annular edge 36 and the bottom surface 44 of the disc 35 results in homogenlzation with the production of a completely uniform size dispersion that isydischarged through the outlet 45 into line 46. In the preferred practice of the invention the rosin size is discharged from valve 34 as a 12% solution.

The concentration of the size solution in the pipe 46 is well below that of gel formation, and therefore the size can safely be diluted with cold water; i. e., with water from the ordinary supply of a paper mill such as that having temperatures of 35-70 F. In order to control the final concentration, however, it is again necessary to provide a flow of Water having a constant predetermined rate, and this is done by an additional feature of the present invention. The cold water supply is admitted through a booster pump 5B which works against a pressure reducing valve 52.- This valve is so constructed as to operate with a constant delivered pressure rather than with a constant back pressure so that the water pressure in the line 53 is always (for example) 35 pounds per square inch, or some other known and constant pressure. The now of water from this line to be admixed with rosin size solution in the line 46 can therefore be controlled accurately by means of a manually operated valve 55, which is identical in its construction and operation with the valve 2I in the hot water line 20. By setting the valve 55 to give a known rate of flow. as indicated by a flow meter 56, and by adjusting Y this flow rate in accordance with the ow of rosin size solution in the line 46 as shown by flow meter 51, the nal concentration of dilute rosin size solution can be adjusted.

The dilute and cooled rosin size solution,I having the desired final concentration, is passed by line 58 into homogenizing valve 60, which is a constant back-pressure valve identical in construction and operation with the valves 3 land 34. The resulting dilute rosin size, which passes to the storage tank 6I through line 62, is both uniform in composition and constant in concentration and is suitable for any of the uses for which rosin size is ordinarily employed in a paper mill.

One lof the principal advantages of the abovedescribed system is that it can be operated automatically and without the necessity of supervision. To accomplish this the dilute rosin sizev storage tank 6I is provided with a float 64 that closes a switch 65 when the quantity of size falls below a predetermined level. When this switch closes it starts the gear pump I and also the cold water booster pump 5I. Similarly, these pumps are stopped when the float-control valve 65 is opened.

When the supply of concentrated rosin size to the heater 5 is shut off, by stoppage of the gear.

pump I, the problem of water evaporation and deposition of solids is encountered. In other words, there is a likelihood thatrthe hot metal of the heater 5 will evaporate water from the residual size remaining therein when the gear pump I is stopped, and this would deposit solid material on the metal surfaces that would become baked to an insoluble condition and would soon plug up the-passages of the heat exchanger. In order to avoid such deposition of solids a hot water line 10 controlled by a solenoid-actuated valve 1I is provided. Steam is admitted to the heating chamber of the heater through a thermostatically controlled valve 12 and a solenoidcontrolled valve 13, and the electrical circuit is so arranged that the valve 13 is closed and the valve 1I is opened when the pump I is stopped. By. this provision the steam-heating compartments of the heat exchanger 5 are immediately flooded with hot water from the line 10 when the gear pump'I is stopped. This cools the interior of the heat exchanger, and deposition and burning of the rosin size by hot metal surfaces is prevented. It will of course be understood that the electrical interlock is such that the valve 13 is opened and the valve Tl Iis closed when the pump l is started up again so that the flow of steam to the heater is resumed.

A protective system for the hot and cold water supply lines is also provided. Valve in the hot water supply line and valve 'I6 in the cold water line 53 are stop control diaphragm valves that remain open so long as there is a predetermined water pressure in the supply lines H and "I8 respectively. These supply lines, in turn, are connected with the cold water line 80 through lines 8| and 82 by means of solenoid valves 83 and 84 which remain open as long as the switch 65 is closed and the pumps I and 5I are in operation. When the pump circuit is open, however, these solenoid valves are closed, which results in closing the stop control valves 15 and 16. It will benoted that these Valves would also close, regardless of the electrical circuit, if the water pressure in the line 80 should fall below a predetermined value. The system of my invention is therefore protected fully against undesired dilution that might otherwise be caused by drainage from the lines during repeated starting and stopping of the supply pumps,

From the foregoing description of a preferred embodiment of my invention it will be seen that all the objects thereof are accomplished. A method is provided wherein a stream of the concentrated rosin size is heated and fed into the mixer at a uniform predetermined rate, which rate can be varied by means of the speed control 2 in order to vary the concentration of the diluted rosin size. In the Venturi mixer 25 the stream of hot size is mingled with a stream of hot water delivered at a uniform predetermined rate such that the rsulting size mixture has a solids content well below that of gel formation. The resulting hot, diluted size suspension is homogenized by passage through the valve 34 in order to disperse any lumps or flocks of gel, after which it is further mingled with a stream of cold water delivered at a uniform predetermined rate such as to produce a solids content of 5% 0r less, depending on the particular requirements of the paper mill. Provision is also made for flooding the heating surfaces of the heater 5 with hot water Whenever the flow of rosin size through the passages thereof is interrupted; for maintaining a uniform supply of constant-temperature hot water from the tank I0, and of cold dilution water in the line 53. Provision is additionally made to interrupt the flow of both hot and cold water to the size dilution system when the ow of rosin size is stopped, whereby excessive dilution from residual water in the system is avoided.

What I claim is: 1. A method for the dilution of a concendelivered at a uniform predetermined rate such that the resulting size mixture has a solids content below that of gel formation and within the range of about 10-20% solids, homogenizing the resulting size, and then mingling the size with a stream of cold water delivered at a uniform predetermined rate such that the solids content of the mixture is reduced to 2-592 and again homogenizing the diluted rosin size.

2. Apparatus for diluting a concentrated rosin size solution comprising in combination a motordriven gear pump for delivering a stream of concentrated rosin size at a predetermined constant rate, a heater containing a passage for said stream of concentrated rosin size and a steam chamber in heat exchange relation therewith, a hot water tank, means for supplying steam to said steam chamber when said gear pump is in operation, means for shutting off the steam and supplying hot water from said tank to the steam chamber when the gear pump is stopped whereby burning of residual rosin size in said heater is prevented, means for mingling and diluting the stream of hot concentrated rosin size from said heater with a stream of hot water from said tank supplied at a predetermined constant rate, a homogenizing valve and means for passing the resulting stream of diluted hot rosin size therethrough, means for admixing the homogenized size solution with cold water supplied at a predetermined constant rate, and a second homogenizing valve and means for passing the diluted and cooled rosin size dispersion therethrough.

3. Apparatus for diluting a concentrated rosin size solution comprising in combination a motordriven gear pump for delivering a stream of concentrated rosin size at a predetermined constant rate, a heater containing a passage for said stream of concentrated rosin size and a steam chamber in heat exchange relation therewith, a hot water tank having an external hot water recirculation system containing a circulating pump, a steam injector and a back pressure valve, a Venturi mixer having a rosin size inlet connected to the rosin size outlet of said heat exchanger and a water inlet connected by a pipe containing a hot water stop control valve yto a point in said hot water recirculation system between the circulating pump and the back presture valve, a homogenizing valve and means for passing hot diluted rosin size from said Venturi mixer therethrough, a second homogenizing valve having an outlet pipe leading to a dilute rosin size storage tank, a dilution pipe connecting the two homogenizing valves; a cold water pipe provided with a cold water stop control valve joining said dilution pipe to a source of cold dilution water at constant pressure, and means for shutting off the steam and substituting hot water. in the steam chamber-of said heat exchanger and for simultaneously closing said hot and cold water stop control valves when the motor-driven gear pump is stopped.

EDGAR A. HOWELL.

No references cited. 

